The technology is also expected to reduce greenhouse emissions by up to 10.3 billion metric tons. These improvements will rely on hybrid technology being in widespread use, and power generation will need to be significantly cleaner to produce than is the case with current power stations. However, if hybrid plug in cars only account for a small proportion of all sales (20% rather than 80% in the first situation) and little has been done to improve the pollution from power plants, the technology is still predicted to save enough carbon dioxide to fill 163 million three-bedroom homes**.

Plug-in hybrids run one-quarter to one-half cleaner than an advanced conventional hybrid electric vehicle and therefore, as long as cleaner power generation is in place, they are likely to play an important role in our future transport systems.